Second messenger pathways involving cAMP regulate a wide variety of cell functions. One of the mediators in this cascade is the type II cAMP- dependent protein kinase A which appears to be targeted to specific subcellular domains by A-kinase anchoring proteins (AKAPs). AKAP120, recently cloned from parietal cell cDNA, is a fragment of the larger AKAP350, now cloned from both rabbit parietal cells as well as human gastric cDNA. In several culture cell lines, AKAP350 localizes the regulatory subunit of A-kinase to centrosomes, and we have recently shown that this localization persists throughout mitosis. In rabbit parietal cells, however, this AKAP appears to be part of a complex of proteins with multiple cytosolic foci. Specifically, the following proposal seeks to 1) determine the structural elements within AKAP350 responsible for targeting of the protein to different subcellular domains in MDCK cells and parietal cells, and 2) identify proteins which interact with AKAP350 in gastric parietal cells. These studies will enhance our understanding of the role of AKAP350 and cAMP-dependent protein kinase in microtubule cell division. These investigations will identify critical aspects of AKAP350 association with the cytoskeleton that may lead to a greater understanding of the regulation of microtubule organization by second messengers.